A modular synthesizer format which falls into the "small format" category. Not to be confused with various standards for industrial and lab instrumentation which use the same name (or with the line of low-cost mixers marketed by…

A synth which is constructed from discrete functional modules (such as VCOs, VCAs, envelope generators, mixers, etc.), which the performer can purchase and install individually as needed to construct any desired configuration. The…

A standard for signal interconnections, widely used in synthesizers and particularly modular synthesizers. The phone jack standard was, as the name suggests, originally developed for use in telephone switchboards. The male jack is…

A signal intended to control some other parameter, such that the value of that parameter corresponds to the input voltage. For instance, a voltage controlled oscillator might have a control voltage input which determines its…

A signal which conventionally represents the pressing and releasing of a key on a keyboard, or some other on/off state, and is most commonly used to activate an envelope generator. Conventionally, a gate signal has two states.…

In the context of a modular synthesizer, the format is a set of parameters which specify the physical and electrical compatibility of a particular manufacturer's modules. Important mechanical parameters include the module height,…

Eurorack Modular??

Some background information about Modular Synthesizers in the
Eurorack Format:

Definition of
Eurorack?

A modular synthesizer format which falls into the "small
format" category. Not to be confused with various
standards for industrial and lab instrumentation which use the same
name (or with the line of low-cost mixers marketed by Behringer
under this name), this Eurorack format calls for
modules of 128.5mm (slightly over 5") height. Horizontal width is
measured in "horizontal pitch", where 1 HP = 5mm (very slightly
less than 0.2"); most manufacturers use a horizontal unit
definition of either 1U = 4HP, or 1U = 6HP. 3.5mm phone
jacks are used for interconnection.

Unlike most formats used by current modular manufacturers, the
Eurorack format calls for ±12V
power (most other current formats use ±15V), in addition
to +5V required by some modules. Unfortunately, the power
connections are not well standardized; the format uses ribbon
cables for power and a two-row ribbon cable connector containing
either 10, 12, or 16 pins. The 16-pin connector uses some of the
extra pins to distribute control voltage and gate signals from a
keyboard to the modules via a common case connection.

Modular
synthesizer?

A synth which is constructed from discrete functional modules
(such as VCOs, VCAs, envelope generators, mixers, etc.), which the
performer can purchase and install individually as needed to
construct any desired configuration. The first practical
synthesizers as we know them today, beginning with the work of
Donald Buchla and Bob Moog in the
early 1960s, were modular in construction.In a
typical modular synth, all inputs and output within each module are
accessible via jacks on the front panel, and are routed by the use
of patch cords; there is no pre-defined routing. (If no patch cords
are plugged in, the modular makes no sound.)

Because of this, modular synths are considered by
many to be the ultimate in complex-sound creativity, as the number
of possible signal routings in any non-trivial configuration is
nearly infinite, and the system is fully open to
interconnection with external devices at any point
in the signal chain. However, this flexibility and lack of
pre-wired connections makes this type of synth difficult to learn
and to play. Also, the modular method of construction is relatively
space- and cost-inefficient, meaning that a large configuration
will require a substantial amount of time, space, and money to set
up. (Among other things, this means that as a practical matter most
modular synths are monophonic, as a polyphonic
setup requires multiple copies of everything.) All current modular
synths employ analog signal routing and most of
the module circuitry is analog, although there are some digital
processing modules available. Modular synths disappeared from the
market in the 1980s, but since about 1997 have made a significant
comeback, with dozens manufacturers currently active in the
market.

Phone
Jack?

A standard for signal interconnections, widely used in
synthesizers and particularly modular synthesizers. The phone jack
standard was, as the name suggests, originally developed for use in
telephone switchboards. The male jack is cylindrical with a pointed
tip and a grooved band near the tip; it has an insulator that
separates the tip area from the barrel of the cylinder (referred to
as the "sleeve"). In use, interconnection cords or patch cords
always have male connectors at both ends, and the equipment being
connected always has female connectors.

There are actually three sizes of standard phone
jacks, but only two are used in synths. The largest size
has the male plug with a barrel diameter of 1/4" (6.35 mm) and is
always referred to as the "quarter inch" jack. This size is
commonly used for audio inputs and outputs on synthesizers and
other musical equipment, and is the standard size for patch
interconnection jacks in the Dotcom and MOTM modular synth formats.
The next smallest size has the male plug with a barrel
diameter of 3.5mm (it is sometimes referred to
incorrectly as the "1/8 inch" jack). In
synthesizers, this size is used mainly as the standard for patch
interconnect in the Eurorack and Frac modular
synth formats. (A third size with a male plug barrel diameter of
2.5mm is rarely seen in any musical gear.)

Phone plugs have the advantages of being inexpensive and fairly
reliable for analog signal connections, and quick to connect and
disconnect. The 1/4" size is known for being very sturdy and
tolerating a lot of abuse; the main disadvantage is that the jacks
take up a lot of space on a panel. The 3.5mm size takes up
less space but tolerates less abuse. A feature of all
types is that the female jacks can be arranged so that they have
internal normalled connections, which is a "default" connection
that is in effect when no plug is inserted in the jack.

Phone plugs and jacks may have two, three, or four separate
contact surfaces. The two-contact type is known as "TS"
(tip-sleeve) and is what is most commonly used
with synths. The three-contact type is known as "TRS"
(tip-ring-sleeve); it is commonly used in studios to support
"balanced line" connections. Some synths have balanced-line outputs
and have jacks that will provide a balanced line when a cord with a
TRS plug is used, or a conventional unbalanced line when a cord
with a TS plug is used. The four-contact "TRRS" type is seldom used
in musical equipment.

Control
Voltage?

A signal intended to control some other
parameter, such that the value of that parameter
corresponds to the input voltage. For instance, a voltage
controlled oscillator might have a control voltage input which
determines its output frequency. In an analog synthesizer designed
according to the principle of voltage control, control
voltages and audio signals are interchangeable, such that,
for instance, the output of a VCO could be used as a control
voltage input to the cutoff frequency of a voltage controlled
filter.

The principles of voltage control were developed in the early
1960s by Don Buchla and Bob Moog,
working independently. Their work was in turn based on some
circuits designed for the RCA Synthesizer in the 1950s, and the
work of Lamonte Young in the 1940s. Voltage control was a major
step forward; prior to that time, synth parameters were usually
controllable only manually by knobs or switches, which severely
limited the playability and expressiveness of the instrument.

Gate
Signal?

A signal which conventionally represents the pressing and
releasing of a key on a keyboard, or some other on/off
state, and is most commonly used to activate an
envelope generator. Conventionally, a gate signal has two
states. When no keys are pressed on the keyboard, the gate is in
the low or inactive state. Pressing a key changes the gate signal
to the active or high state, and it remains in that state as long
as the key is pressed. (See ADSR for a description
of how a typical envelope generator uses a gate signal.) The gate
signal is by definition monophonic; on a
monophonic synth, generally the gate signal will be in the high
state as long as any key on the keyboard is pressed. However, true
polyphonic synths extend the concept so that a gate signal exists
(conceptually if not in actual implementation) for each voice. Gate
signals can also represent the state of switches and other events
with two states. Compare with trigger.

Format?

In the context of a modular synthesizer, the format is a set of
parameters which specify the physical and electrical
compatibility of a particular manufacturer's modules.
Important mechanical parameters include the module
height, the width of one horizontal unit (modules are
usually designed in multiples of a basic unit width, referred as
"1U", in order to avoid gaps between modules), and the pattern of
mounting holes used for the screws that attach the module to the
case's mounting rails. Important electrical
parameters include the power supply voltages
required, the type of connector used for connecting to the
power supply, the voltage level of a trigger
signal, and the type of jacks used for
patch cords. The three most commonly used types of jacks are the
1/4" phone jack, the 3.5mm phone jack (often
incorrectly referred to as a 1/8" jack), and the banana jack. There
are grounding considerations that must be addressed when a modular
which uses banana jacks is to be interconnected with another synth,
or other equipment, which uses some other type of jack.

The formats used by modular synthesizers currently in production
are often divided into categories, referred to as "small
format" and "large format". Small-format
modulars take up less space (the amount of space required
is often a consideration when considering the purchase of a
modular); they gain this space in part by using smaller knobs and
jacks, which some users find uncomfortable to use. Large-format
modulars generally use larger, easier-to-use knobs and sturdier
jacks and other components, but they take up more room and are
harder to move. The categories, with the most common formats used
by current modular systems, are:

Small format:

Eurorack
Frac

Large format:

Dotcom, aka Moog Units or MU
MOTM
Modcan-A

ADSR

The most common type of envelope generator,
producing a four-segment signal corresponding to four phases of a
note’s dynamics (in the usual case where the signal is used to
control a voltage controlled amplifier that determines the note’s
volume). Each letter of the acronym stands for one of the
four phases, in time order: attack, decay,
sustain, and release. A typical ADSR allows the performer
to set rise/fall rates for attack, decay, and release, and a level
for the sustain phase.(Fancier envelope generators may have more
settings or more operational phases.) Conventionally, an
ADSR is triggered by the leading edge of a gate
signal. The gate going high initiates the attack phase, in which
the ADSR’s output rises from the zero level to a set maximum level
at the chosen rate.This is immediately followed by the decay phase,
in which the output falls from the maximum level to the sustain
level. The output remains at the sustain level until the gate
signal goes back low.At that point the release phase executes, and
the ADSR output falls from the sustain level to its zero level at
the chosen rate. Options often found on ADSRs are an input that
allows all of the rates to be scaled (a function often tied to
keyboard velocity, for acoustic instrument simulation), and a
switch that allows making the rise/fall rates exponential with time
instead of constant. (Such is often useful for percussion
sounds.)